The subject matter disclosed herein relates generally to Magnetic Resonance Imaging (MRI) systems, and more particularly to methods and systems for reducing acoustic noise in MRI systems.
MRI is a medical imaging modality that generates images of the inside of a human body without using x-rays or other ionizing radiation. MRI uses a main magnet to create a strong, uniform, static magnetic field (i.e., the “main magnetic field”) and gradient coils to produce smaller amplitude, spatially varying magnetic fields when a current is applied to the gradient coils. When a human body, or part of a human body, is placed in the main magnetic field, the nuclear spins that are associated with hydrogen nuclei in tissue water become polarized. The magnetic moments that are associated with these spins become preferentially aligned along the direction of the main magnetic field, resulting in a small net tissue magnetization along that axis (the “z axis,” by convention) and the gradient coils encode the MR signal.
At least some MRI systems generate a relatively high magnetic field strength using the main magnet. Additionally, the MRI system may be operated to perform relatively high-speed gradient coil current switching. In some cases, an interaction between the main magnetic field and the current switching in the gradient coils may generate vibrations in the gradient coil. As a result, the vibrations generated by the gradient coil, and potentially, a gradient coil support structure may create sound waves. High acoustic Sound Pressure Levels (SPLs) may be created in and/or around the MRI system due to these sound waves. Moreover, generating high-quality images by using relatively fast scan times may also generate acoustic noise of a substantially high level. The acoustic noise may therefore cause a decrease in patient comfort or an increase in patient anxiety during the image acquisition process.